package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.*;

@Component
@Slf4j
public class CacheClient {

    private  final StringRedisTemplate stringRedisTemplate;

    public  CacheClient(StringRedisTemplate stringRedisTemplate)
    {
        this.stringRedisTemplate =stringRedisTemplate;
    }

    public void  set(String key, Object value, Long time, TimeUnit unit)
    {
        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);

    }

    //逻辑过期
    public void  setWithLogicalExpire(String key, Object value, Long time, TimeUnit unit)
    {
        //设置逻辑过期
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));

        //写入redis
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));

    }

    public <R,ID> R queryWithPassThrough(String keyPrefix , ID id,
                                         Class<R> type, Function<ID,R> dbFallback,Long time,TimeUnit unit)
    {
        String key = keyPrefix + id;
        //1从redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2判断是否存在
        if (StrUtil.isNotBlank(json)) {
            //3存在，直接返回,转成Java对象返回
            return JSONUtil.toBean(json,type);
        }
        //判断是否为null,前面isNotblank只判断里面有值，这里如果不为空就为空串
        if (json != null)
        {
            return null;
        }
        //4不存在,根据id查询数据库
        R r = dbFallback.apply(id);
        //5不存在返回错误
        if (r == null) {
            //5.1将空值写入redis
            stringRedisTemplate.opsForValue().set(key,"",CACHE_NULL_TTL, TimeUnit.MINUTES);
            //5.2返回错误信息
            return null;
        }
        //6存在，写入redis，返回
        this.set(key,r,time,unit);
        return r;
    }


    //获取互斥锁
    private  boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    //释放锁
    private  void  unLock(String key)
    {
        stringRedisTemplate.delete(key);
    }


    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);

    public <R ,ID> R queryWithLogicalExpire(String keyPrefix,ID id,
                                            Class<R> type,Function<ID,R> dbFallback,Long time, TimeUnit unit)
    {
        String key = keyPrefix + id;
        //1从redis查询商户缓存
        String json = stringRedisTemplate.opsForValue().get(key);
        //2判断是否存在
        if (StrUtil.isBlank(json)) {
            //3不存在，返回空
            return null;
        }
        //4 命中，需要先把json反序列化对象
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(), type);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5. 判断是否过期
        if (expireTime.isAfter(LocalDateTime.now()))
        {
            //5.1未过期，直接返回店铺信息
            return  r;
        }
        //5.2 已过期，需要缓存重建
        //6. 缓存重建
        //6.1 获取互斥锁
        String lockKey=LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        //6.2判断是否获取锁
        if (isLock)
        {
            //6.3 TODO 成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() ->{
                try {
                    //查询数据库
                    R r1 = dbFallback.apply(id);
                    //写入redis
                    this.setWithLogicalExpire(key,r1,time,unit)
                    ;
                } catch (Exception e) {
                    throw new RuntimeException(e);
                }finally {
                    //释放锁
                    unLock(lockKey);
                }
            });
        }
        //6.4 返回过期的商品信息
        return r;
    }





}
